1. Field of the Invention
This invention relates to the field of the precision separation of relatively small-diameter vitreous cylinders into cylinders of shorter lengths.
2. Description of Prior Art
There are various industries which require large volumes of short lengths of glass tubes and rods having cylindrical external surfaces. For example, vast numbers of automobile fuses are manufactured employing short-length glass tubes. Other examples include glass cases for diodes, capacitors and reed switches.
Until the advent of the present apparatus and method, the ways of separating long lengths of extruded glass tubing (and rods) into desired short lengths were unsatisfactory for various reasons. Two of such prior-art ways will now be discussed briefly.
To achieve precision separation of glass tubes into desired lengths, so that there are no substantial chipped ends, etc., it is now conventional to "pot" somewhat longer lengths of tubes in synthetic resin or wax. For example, a tube length approximately four or five inches long is filled with and surrounded by the synthetic resin, and the latter is allowed to harden. Then, with the internal and external support provided by the resin, there is no substantial chipping and breakage when diamond wheels are employed to make the desired separations. After subdividing of the tubes is completed, the synthetic resin is removed by heating and then by an extensive cleaning process.
The described potting and separation operations are productive of precision-cut glass tubes but are extremely laborious, slow, expensive, etc. As a further disadvantage, the potting substance tends to accelerate wearing-out of the expensive diamond wheels, since such wheels must grind through the potting material as well as the glass.
A second way of separating glass tubes into short lengths, and one which does not require potting, makes use of the thermal shock principle. A machine of this type uses a multiplicity of rotating chucks each of which contains a length of glass tubing. The tubes move past burner wheels so that separations result as the result of thermal shocks. At any particular time, only one separation is occurring in each tube. This type of machine is extremely large and heavy, with many moving parts, yet it cannot subdivide glass tubes with the precision, speed, cleanness, low energy requirement, etc., achieved by the present method and apparatus.